Marcus von Appen wrote:
It is - at least for me - no error, if I try to unlock a surface that a) has no locks or b) is locked by something else.
But consider the following sequence: 1. Something else locks the surface. 2. I lock the surface -- nothing happens, it's already locked. 3. Something else unlocks the surface. 4. I unlock the surface -- nothing happens, it's already unlocked. In between 3 and 4, I think the surface is locked, but it's not. -- Greg